DE102015209173B4 - METHOD FOR PRODUCING AN OBJECTIVE FOR A LITHOGRAPHIC PLANT - Google Patents

Abstract

A method of producing a lens (104) for a lithography apparatus (100), comprising the following steps:
a) providing at least a first and a second partial objective (200A, 200B), wherein the at least one first partial objective (200A) comprises a plurality of optical elements (202A) and the at least one second partial objective (200B) comprises at least one optical element (202B) the at least one first and second partial objective (200A, 200B) each have a beam path (204A, 204B) which is non-homocentric on the input and / or output side (206, 210, 212) of a respective partial objective (200A, 200B) is
b) transmitting at least one first light beam (500, 602) along a respective beam path (204A, 204B) of the at least one first and second sub-objective (200A, 200B) and detecting the at least one first light beam (500, 602) behind a respective sub-objective ( 200A, 200B),
c) determining at least one optical characteristic of a respective partial objective (200A, 200B) on the basis of the detected, at least one first light beam (500, 602),
d) adjusting the plurality of optical elements (202A) of the first partial objective (200A) and the at least one optical element (202B) of the second partial objective (200B) in dependence on the determined optical characteristic, and
e) assembling the at least one first and second partial objective (200A, 200B) to produce the objective (104).

Description

The present invention relates to a method for producing a lens for a lithography system.

Microlithography is used to fabricate microstructured devices such as integrated circuits. The microlithography process is performed with a lithography system having an illumination system and a projection system. The image of a mask (reticle) illuminated by means of the illumination system is projected by the projection system onto a substrate (eg a silicon wafer) coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection system in order to project the mask structure onto the photosensitive layer Transfer coating of the substrate.

Driven by the quest for ever smaller structures in the manufacture of integrated circuits, EUV lithography systems are currently being developed which use light with a wavelength in the range of 0.1 nm to 30 nm, in particular 13.5 nm. In such EUV lithography equipment, because of the high absorption of most materials of light of this wavelength, reflective optics, that is, mirrors, must be used instead of - as before - refractive optics, that is, lenses.

The mirrors can z. B. on a support frame (English: force frame) and at least partially designed to be manipulated to allow movement of a respective mirror in up to six degrees of freedom and thus a highly accurate positioning of the mirror to each other, especially in the pm range. Thus, occurring during operation of the lithographic system changes in the optical properties, eg. B. due to thermal influences, be compensated.

Conventionally, lithography equipment is built up by the manufacturer. This includes in particular a positioning and alignment of the mirror to each other. "Positioning" means a movement of a corresponding mirror in up to three translatory degrees of freedom. "Aligning" means moving a corresponding mirror in up to three rotational degrees of freedom. The positioning and alignment of the mirrors is repeated until an image, which is generated on the input side of the projection objective of the lithography system, is correctly imaged on the output side of the objective. Subsequently, the mirrors are fixed in their respective position. This completes the qualification of the lithography system.

In order to bring such a lithography system to the customer, it has to be disassembled into its individual parts, due to its large dimensions. The customer then has to repeat the above-described process of positioning and aligning the mirrors. This process is very complex - not only because of the large number of positioning and alignment steps, but also because of the increasing size of the individual mirrors (in some cases larger than 2 m in diameter) and a correspondingly large weight of the mirror.

Therefore, approaches have been known from the prior art to simplify the process described above.

For example, describes the JP 2004-128307 A a projection lens, which includes two partial lenses. The partial lenses each contain three mirrors. Between the two partial lenses an intermediate image plane is formed. Thus, the mirrors within each sub-objective can be positioned and aligned with each other. The intermediate image plane is used to check the correct position and orientation of the mirrors. After qualifying a respective partial objective, the partial objectives are assembled to form the objective.

The US 2011/0001945 A1 describes an approach in which a projection lens is also divided into several sub-objectives. The partial lenses are positioned and aligned with each other at the manufacturer. The position and orientation is checked and stored by means of appropriate sensors. For transport to the customer, the lens is again disassembled into its partial lenses. At the customer's site, the lens can be easily reassembled from the component lenses using the sensors and stored data, restoring the original positioning and alignment of the component lenses to each other.

The WO 2006/125609 A1 describes an interferometer for determining the relative position of a first optical element to a second optical element.

Against this background, an object of the present invention is to provide an improved method for producing a lens for a lithography system.

Accordingly, a method for producing a lens for a lithography system is provided, comprising the following steps: a) providing at least one first and second partial objective, wherein the at least one first partial objective of a plurality of optical elements and the at least one the second partial objective comprises at least one optical element, the at least one first and second partial objective each having a beam path which is not formed homocentrically on the input and / or output side of a respective partial objective, b) transmitting at least one first light beam along a respective optical path of the first c) determining at least one optical characteristic of a respective partial objective on the basis of the detected, at least one first light beam, d) adjusting the plurality of optical elements of a respective partial objective as a function of the determined optical characteristic, and e) assembling the at least one first and second partial objective for the production of the objective.

The finding underlying the present invention is based on the fact that it is not always possible to subdivide an objective into sub-objectives in such a way that intermediate image planes are located between the sub-objectives. Rather, it may be advantageous, for example, for the sake of creating partial lenses with favorable geometry or low packaging dimensions, to divide a corresponding objective into partial lenses, with no intermediate image plane at the interfaces between any two lenses. In such cases, the beam path between two corresponding partial lenses is usually non-homocentric. This means that the light rays can not be reduced to one point and are not parallel.

So far, a problem has been, in the case of such a non-homocentric beam path, to visually qualify a respective partial objective, i. H. in particular, to perform the positioning and alignment of the respective mirrors in such a way that a correct imaging by means of the objective is produced after the joining of the partial objectives to form the objective.

The solution described here makes possible precisely such a qualification of a partial objective with non-homocentric beam path. For this purpose, in each case a first light beam is transmitted by the first and second partial objective and detected according to a respective partial objective. From the detected first light beam, an optical characteristic of a respective partial objective is determined. The adjustment of the optical elements of the first and second partial objective takes place as a function of the determined optical characteristic. The optical characteristic of the at least one first light beam may relate, for example, to a position, an angle and / or a wavelength thereof on the output side of the corresponding partial objective. Furthermore, the optical characteristic may include a comparison of the position, the angle and / or the wavelength with a corresponding reference value.

The splitting of the objective into a plurality of partial objectives advantageously leads to a reduction in the complexity of the adjustment process, as explained in more detail below. "Adjustment" encompasses positioning and / or alignment of the corresponding optical element. "Positioning" means moving the corresponding optical element in up to three translatory degrees of freedom. "Aligning" means moving the corresponding optical element in up to three rotational degrees of freedom.

As a measure of the complexity, for example, the number of possible original states is understood. Using the example of the decomposition of an eight-component objective into three partial objectives, the following is used to calculate the reduction of possible original states:

Let N ₁ , N ₂ , N ₃ , ... N _{k be} the number of possible positioning and alignment states of the optical elements 1, 2, 3, ... k, where k = 8. Let M _{1 2} and M _{2 3} the number of possible original states in the adjustment of the partial lenses to each other, ie partial lens 1 to partial lens 2 and partial lens 2 to partial lens 3. In a Gesamtobjektivjustage N ₁ · N ₂ · N ₃ · ... N ₈ original states are possible. In the case of the modularized adjustment, the number of possible initial states is: N ₁ .N ₂ .N ₃ + N ₄ .N ₅ .N ₆ + N ₇ .N ₈ + M _{1 2} .M _{2 3} . Assuming for the sake of simplicity that the number of possible original states are the same for all optical elements and partial lenses, this number being called N here, then a reduction of the original state number from N ⁸ to only 2 · N ³ + 2 · N ² follows.

In principle, the first partial objective may contain two or more optical elements. The second sub-objective may include one or more optical elements. Typically, a lens contains six, seven, eight, or nine mirrors. These can be advantageously divided, for example, three partial lenses. This results in the corresponding simplification of the assembly as exemplified above.

According to one embodiment, the at least one first light beam is detected by a detection device on which it generates a light point, wherein the determination of the at least one optical characteristic comprises a comparison of the light point with a reference light point. The step of comparing can for example be done automatically by means of a suitable computer device.

According to another embodiment, a position of the light spot with a position of Reference light point compared. This results in a simple process.

According to a further embodiment, at least a first and a second light beam spaced therefrom are transmitted along a respective beam path of the at least one first and second partial objective and detected behind a respective partial objective, wherein the at least one optical characteristic is determined on the basis of the detected, first and second light beams , By using two light beams spaced apart from each other, they each take a different course along the beam path along a respective partial objective, so that more information about a particular partial objective can be obtained.

According to a further embodiment, the at least one first and second light beam is detected by a detection device on which the at least one first and second light beam generate a light spot pattern, wherein determining the at least one optical characteristic comprises comparing the light spot pattern with a reference light spot pattern. This step of comparing the light spot pattern with a reference light spot pattern can also be done automatically. For example, an adjustment of the optical elements of the corresponding partial objective can be repeated until an average distance of the light spots of the light spot pattern to reference light spots of the reference light spot pattern is minimal.

According to a further embodiment, the at least one first and the second light beam spaced therefrom is generated by moving a light source between two positions. Moving the light source between the two positions can be done automatically.

According to one embodiment, the light source is moved between the two positions by means of a robot. This results in a simple, repeatable process.

According to a further embodiment, the at least one first and the second light beam spaced therefrom are generated by providing two spaced-apart light sources. For example, the two spaced-apart light sources can be generated by irradiating a mask with at least two light passages with a light source.

According to a further embodiment, the at least one optical characteristic of at least one partial objective is determined using a deflektometric measuring method. Deflectometry here refers to the non-contact detection or measurement of reflective surfaces. Techniques from photometry, radiometry, photogrammetry, laser scanning or laser distance measurement are used.

In accordance with a further embodiment, at least one light source for generating the at least one first light beam and a mask illuminated by it are arranged in front of the at least one partial objective and a detection device for detecting the at least one first light beam behind the corresponding partial objective. This results in a simple measurement setup.

According to a further embodiment, the at least one optical characteristic of at least one partial objective is determined using a method for wavefront measurement. In this case, "wavefront measurement" means in particular a detection of the local inclination of the wavefront with respect to a reference. The inclination or a corresponding displacement of points of light can be measured by means of position-sensitive detectors which, for example, contain the detection device. In particular, a Shack-Hartmann sensor can be used for wavefront measurement.

According to a further embodiment, at least one light source for generating the at least one first light beam and a mask illuminated by the latter are arranged in front of the at least one partial objective for the method for wavefront measurement. Furthermore, a correction optics for correcting the at least one first light beam is provided. In addition, a detection device for detecting the at least one first, corrected light beam is arranged behind the corresponding partial objective. The correction optics can be arranged in front of or behind the partial objective and are set up to filter out information suitable for the detection device from the at least one first light beam.

According to a further embodiment, the correction optics detects a microlens array or a pinhole grid. By means of the microlens array or the pinhole screen, a characteristic light spot pattern can be generated from the incident wavefront, which in turn can be easily compared with a corresponding reference light spot pattern.

According to a further embodiment, the correction optics has a computer-generated hologram. "Computer Generated Hologram" means that a corresponding holographic interference pattern is generated digitally. This generating may include, for example, that Holographic interference pattern is calculated digitally and then printed on a mask or a film. The illumination of the mask or of the film is effected by the at least one first and / or second light beam. Alternatively, the computer generated hologram may also be generated using partial or full use of a holographic 3D screen. By means of the computer-generated hologram, the at least one first and / or second light beam can be modified in such a way that information that is favorable for the detection device is generated. For example, the modification may be such that "artificially" an intermediate image plane is generated at the output side of the corresponding sub-objective. A comparison of the input-side image with its corresponding image in the intermediate image plane then allows a simple adjustment of the optical elements of the corresponding partial objective until image and image correspond.

According to a further embodiment, the correction optics each have a computer-generated hologram for each light beam. When using correction optics comprising a computer-generated hologram, a separate computer-generated hologram can be used for each field point used. As a result, the amount of information available for the readjustment can be significantly increased. The computer-generated holograms can be arranged behind the field points.

According to a further embodiment, the computer-generated hologram is arranged in front of the microlens array or the pinhole grid. This means that the at least one first and / or second light beam initially passes through the computer-generated hologram and then passes through the microlens array or the pinhole grid to the detection device.

According to a further embodiment, the computer-generated hologram is configured to parallelize the at least one first and second light beam. The detection and evaluation of parallel light or the determination of a corresponding optical characteristic is simple. In particular, this provides the possibility of providing an intermediate image plane on the output side at a corresponding partial objective.

According to a further embodiment, the at least one optical characteristic of at least one partial objective is determined in a first step using the method for wavefront measurement without computer-generated hologram and in the second step with computer-generated hologram. After the first step as well as after the second step, preferably an adjustment of the optical elements of the corresponding partial objective takes place. Thus, a rough adjustment (without computer-generated hologram) and then a fine adjustment (with computer-generated hologram) take place.

According to a further embodiment, the detection device is a ground glass and / or an electronic chip. For example, a CMOS or CCD chip can be used as the electronics chip.

According to a further embodiment, the plurality of optical elements of the first partial objective and the at least one optical element of the second partial objective are fixed after step d). The fixation ensures that no change in the position and / or orientation of the optical elements takes place even when the individual partial lenses are transported, in particular to the customer.

According to a further embodiment, the plurality of optical elements of the first partial objective and / or the at least one optical element of the second partial objective can be actuated between a first position and a second position and / or orientation during operation of the lithography apparatus, wherein step c) in the first and second Position and / or alignment is performed. Thus, a dynamic qualification of a respective partial objective can also be carried out. Correspondingly, corrections as well as repairs with respect to the corresponding actuators or travel paths of the actuatable optical elements can already be carried out during the qualification of a respective partial objective. This results in a further reduction of the assembly work.

According to a further embodiment, an imaging optical characteristic of the produced objective at the operating wavelength is determined after step e). In principle, the at least one first and / or second light beam may have the operating wavelength or other wavelengths. The operating wavelength depends on the type of lithography system. The lithography system may preferably be an EUV or DUV lithography system. EUV stands for "extreme ultra violet" and refers to a wavelength of the working light or the operating wavelength between 0.1 and 30 nm. DUV stands for "deep ultra violet" and denotes a working light wavelength between 30 and 250 nm. In one step After joining the partial objectives to form the objective, an output-side image is compared with an input-side image, the correct functioning of the objective as a whole can be ensured. The objective is preferably a projection objective of a lithography system.

According to a further embodiment, depending on the determined imaging optical characteristic, a post-processing of surfaces or an actuation of one or more of the optical elements of the at least one first or second partial objective takes place. Thus, a further correction of the beam path can be made even after production of the lens.

According to a further embodiment, an interface in the beam path between the at least one first and second partial objective subdivides a distance between an optical element of the first partial objective and an optical element of the second partial objective longer than the longest distance between each two adjacent optical elements of the at least one first and second sub-objective. "Interface" means the area in which the at least first and second sub-objectives are assembled to form the lens. Such a selected interface may be favorable for structural or space reasons.

According to a further embodiment, at least three partial lenses are provided. The third partial objective may have at least one or more optical elements. The comments made above on the first and second partial objective apply correspondingly to the third partial objective. Of course, more than three partial lenses, for example, five partial lenses could be provided.

According to a further embodiment, the plurality of optical elements of the first partial objective and / or the at least one optical element of the second partial objective are mirrors and / or lenses. The lenses are preferably arranged in single passage, i. H. the light passes through them only in one direction.

According to a further embodiment, two or more partial lenses are combined to form a partial objective. As a result, new partial lenses are built, which in turn can be measured with the methods described above. The summarizing to new partial lenses may mean that the individual partial lenses are arranged and fixed to one another.

According to a further embodiment, the steps a) to e) are repeated with the combined partial objective. Advantageously, a summarized partial objective can also be measured by the methods described above.

Furthermore, a measuring device for determining an optical characteristic of a partial objective for a lithography system is provided. The measuring device comprises a transmitting device for transmitting at least one first light beam along a beam path of the partial objective, a correction optics having a computer-generated hologram, a detection device for detecting the at least one first light beam, and a determining device for determining at least one optical characteristic of the partial objective based on the detected, at least a first light beam. As described above, the use of a computer-generated hologram allows favorable information to be generated for the detector.

The features, embodiments and advantages described in relation to the method apply correspondingly to the measuring device.

Further possible implementations of the invention also include not explicitly mentioned combinations of features or embodiments described above or below with regard to the exemplary embodiments. The skilled person will also add individual aspects as improvements or additions to the respective basic form of the invention.

• 1A zeigt eine schematische Ansicht einer EUV-Lithographieanlage;
• 1B zeigt eine schematische Ansicht einer DUV-Lithographieanlage;
• 2 zeigt schematisch ein Projektionsobjektiv einer Lithographieanlage umfassend ein erstes und ein zweites Teilobjektiv;
• 3A zeigt das erste Teilobjektiv aus 2;
• 3B zeigt das zweite Teilobjektiv aus 2;
• 4 zeigt eine Ausführungsform, die ebenfalls ein Teilobjektiv im vorliegenden Sinne darstellt;
• 5A und 5B zeigen perspektivisch bzw. schematisch ein deflektometrisches Messverfahren gemäß einer Ausführungsform;
• 6A und 6B zeigen perspektivisch bzw. schematisch ein Verfahren zur Wellenfrontmessung gemäß einer Ausführungsform;
• 7A und 7B zeigen perspektivisch bzw. schematisch das Verfahren gemäß den 6A und 6B mit einem zusätzlich vorgesehenen computergenerierten Hologramm; und
• 8 zeigt ein Flussdiagramm eines Verfahrens gemäß einer Ausführungsform.

Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the embodiments of the invention described below. Furthermore, the invention will be explained in more detail by means of preferred embodiments with reference to the attached figures.

• 1A shows a schematic view of an EUV lithography system;
• 1B shows a schematic view of a DUV lithography system;
• 2 schematically shows a projection lens of a lithographic system comprising a first and a second partial objective;
• 3A shows the first partial lens 2 ;
• 3B shows the second partial lens 2 ;
• 4 shows an embodiment which also represents a partial objective in the present sense;
• 5A and 5B show perspectively or schematically a deflectometric measuring method according to an embodiment;
• 6A and 6B show in perspective and schematically a method for wavefront measurement according to an embodiment;
• 7A and 7B show in perspective and schematically the method according to the 6A and 6B with an additionally provided computer generated hologram; and
• 8th shows a flowchart of a method according to an embodiment.

Unless otherwise indicated, like reference numerals in the figures denote like or functionally identical elements. It should also be noted that the illustrations in the figures are not necessarily to scale.

1A shows a schematic view of an EUV lithography system 100A which is a beam shaping and illumination system 102 and a projection system 104 includes. EUV stands for "extreme ultraviolet" (Engl.: Extreme ultraviolet, EUV) and refers to a working light wavelength between 0.1 and 30 nm. The beam shaping and illumination system 102 and the projection system 104 are each provided in a vacuum housing, wherein each vacuum housing is evacuated by means of an evacuation device, not shown. The vacuum housings are surrounded by a machine room, not shown, in which the drive devices are provided for the mechanical method or adjustment of the optical elements. Furthermore, electrical controls and the like may be provided in this engine room.

The EUV lithography system 100A has an EUV light source 106A on. As an EUV light source 106A For example, a plasma source or a synchrotron can be provided, which radiation 108A in the EUV range (extreme ultraviolet range), ie in the wavelength range from 0.1 nm to 30 nm, for example. In the beam-forming and lighting system 102 becomes the EUV radiation 108A bundled and the desired operating wavelength from the EUV radiation 108A filtered out. The from the EUV light source 106A generated EUV radiation 108A has a relatively low transmissivity by air, which is why the beam guiding spaces in the beam-forming and lighting system 102 and in the projection system 104 are evacuated.

This in 1A illustrated beam shaping and illumination system 102 has five mirrors 110 . 112 . 114 . 116 . 118 on. After passing through the beam shaping and lighting system 102 becomes the EUV radiation 108A on the photomask (English: reticle) 120 directed. The photomask 120 is also designed as a reflective optical element and can be outside the systems 102 . 104 be arranged. Next, the EUV radiation 108A by means of a mirror 136 be directed to the photomask. The photomask 120 has a structure which, by means of the projection system 104 reduced to a wafer 122 or the like is mapped.

The projection system 104 has six mirrors M1 - M6 for imaging the photomask 120 on the wafer 122 on. In this case, individual mirrors M1 - M6 of the projection system 104 symmetrical to the optical axis 124 of the projection system 104 be arranged. It should be noted that the number of mirrors of the EUV lithography system 100A is not limited to the number shown. It can also be provided more or less mirror. Furthermore, the mirrors are usually curved at the front for beam shaping.

1B shows a schematic view of a DUV lithography system 100B which is a beam shaping and illumination system 102 and a projection system 104 includes. DUV stands for "deep ultraviolet" (English: deep ultraviolet, DUV) and refers to a wavelength of working light between 30 and 250 nm. The beam shaping and illumination system 102 and the projection system 104 are surrounded by a machine room, not shown, in which the drive devices are provided for the mechanical method or adjustment of the optical elements. The DUV lithography system 100B also has a control device 126 for controlling various components of the DUV lithography system 100B on. In this case, the control device 126 with the beam shaping and illumination system 102 , a DUV light source 106B , a holder 128 the photomask 120 (English: reticle stage) and a holder 130 of the wafer 122 (Engl .: wafer stage) connected.

The DUV lithography system 100B has a DUV light source 106B on. As a DUV light source 106B For example, an ArF excimer laser can be provided, which radiation 108B emitted in the DUV range at 193 nm.

This in 1B illustrated beam shaping and illumination system 102 directs the DUV radiation 108B on a photomask 120 , The photomask 120 is designed as a transmissive optical element and can be outside the systems 102 . 104 be arranged. The photomask 120 has a structure which, by means of the projection system 104 reduced to a wafer 122 or the like is mapped.

The projection system 104 has several lenses 132 and / or mirrors 134 for imaging the photomask 120 on the wafer 122 on. This can be individual lenses 132 and / or mirrors 134 of the projection system 104 symmetrical to the optical axis 124 of the projection system 104 be arranged. It should be noted that the number of lenses and mirrors of the DUV lithography system 100B is not limited to the number shown. There may also be more or fewer lenses and / or mirrors. In particular, points the beamforming and lighting system 102 the DUV lithography system 100B several lenses and / or mirrors. Furthermore, the mirrors are usually curved at the front for beam shaping.

Hereinafter, referring first to the 2 and 8th a method for producing in particular the projection lens 104 at a lithography plant 100 according to the 1A or 1B explained in more detail. The projection lens 104 is hereby synonymous synonymous as a projection system 104 designated.

The projection lens 104 consists, for example, of two partial lenses 200A . 200B together. Just as well could the projection lens 104 but also composed of three, four, five or more partial lenses. The representation of the optical elements 200A . 200B in the projection lens 104 of the 2 ff. is opposite to the representation of 1A and 1B heavily schematized.

A respective partial lens 200A . 200B includes several optical elements 202A . 202B , which may be formed for example as mirrors and / or lenses. An optical path within a respective partial objective 200A . 200B is designated 204A, 204B.

The two partial lenses 200A . 200B are via an interface 206 releasably connectable to each other. 2 shows the assembled state of the two partial lenses 200A . 200B in which she the assembled projection lens 104 form. This results in a continuous beam path 208 , which the partial beam paths 204A . 204B includes. The beam path 208 leads from an input page 210 of the projection lens 104 over the optical elements 202A , over the interface 206 , about the optical elements 202B to the exit side 212 of the projection lens 104 , The entrance page 210 of the projection lens 104 at the same time forms the input side of the partial objective 200A , the interface 206 forms both the output side of the partial lens 200A as well as the input side of the partial lens 200B , The exit side 212 of the projection lens 104 also forms the output side of the partial objective at the same time 200B ,

The entrance and exit side 210 . 212 have a homocentric beam path, so that an image, in particular the structured mask 120 (please refer 1A ) on the wafer 122 is shown.

In the present case, however, the optical elements 202A respectively. 202B a respective partial lens 200A . 200B be adjusted separately, for example, the manufacturer of the lithographic system 100 , The so qualified partial lenses 200A . 200B are then transported to the customer and there to the projection lens 104 assembled.

Therefore, in a first method step 801 (see 8th ) the first and second partial objective 200A . 200B provided as in the 3A and 3B shown. The beam paths of these partial lenses 200A . 200B are due to the chosen course of the interface 206 on the output side of the partial lens 200A or on the input side of the partial objective 200B not homocentric.

the interface 206 may preferably be in a part of the beam path 208 in which the distance between two adjacent optical elements 202A . 202B is greater than the direct distance between any other optical elements 202A . 202B in the projection lens 104 , This longest distance is in 2 denoted by a (does not correspond to the representation of 2 since this is not true to scale, in particular).

Only supplementary is in 4 a partial lens 400 which also represents a partial objective in the present sense, although it emerged by changing the neighborhoods of the optical elements. In the case of 4 were compared to the partial lenses according to the 3A and 3B the lenses 202A omitted. By definition, when disassembling and assembling the partial lenses 200A . 200B the neighborhood relationships of the optical elements 202A . 202B not changed.

8th now shows a method step 802. In method step 802 at least a first light beam, in 5B exemplified by 500, along the beam path 204A of the first partial lens 200A sent and behind the partial lens 200A detected.

In a step 803, an optical characteristic of the partial objective subsequently becomes 200A based on the detected, at least a first light beam 500 determined.

In a step 804, the plurality of optical elements become 202A of the first partial lens 200A adjusted, ie positioned and / or aligned. The adjustment can of course only one or more of the optical elements 202A of the first partial lens 200A affect. The adjustment takes place in dependence on the determined optical characteristic. After this, a fixation of the optical elements 202A in their respective positions.

The foregoing steps will now be with respect to the second sub-objective 200B repeated. Ie. in step 802, the at least one light beam 500 along the beam path 204B of the second partial lens 200B sent and behind the second partial lens 200B detected. Subsequently, in the step 803 an optical characteristic of the second partial objective 200B based on the detected, at least a first light beam 500 determined. In the step 804 become the optical elements 202B of the second partial lens 200B adjusted depending on the determined optical characteristic and finally fixed.

In the step 805 become the first and second partial objective 200A . 200B for the production of the projection lens 104 together.

Of course, the above steps could 801 to 804 also be carried out in parallel. That is, the optical qualification of the two partial lenses 200A . 200B happens at the same time. Instead of the projection lens 104 Of course, another lens can be made.

The steps 802 and 803 are illustrated below in detail by means of three different methods, wherein the 5A and 5B a deflektometric measuring method, the 6A and 6B a method for wavefront measurement and the 7A and 7B illustrate a method of wavefront measurement with the aid of a computer-generated hologram.

5A shows in a perspective view of the first part of the lens 200A in perspective view. The first partial lens 200A is in a measuring device 502 arranged the steps 802 and 803 performs.

The measuring device 502 includes a light source 504 , for example a laser, and a mask 506 in front of the entrance side 210 of the partial lens 200A , The light source 504 generates a beam of light 500 (For example, a narrow beam of light, in particular a laser beam). The light beam 500 falls on the mask 506 , ie it illuminates. The mask 506 can be structured such that it filters out a defined portion of the light beam, so in particular generates collimated or prepared test beams. In particular, the mask 506 also be set up to create a starry sky.

After passing the mask 506 occurs the light beam 500 through the partial lens 200A Through, happens the multiple optical elements 202A (see also 5B ) and leaves the partial lens 200A again at the exit. After that, the light beam hits 500 to a detection device 508 , The detection device 508 includes, for example, a ground glass 510 and behind it a camera 512 which may itself have an objective, not shown.

The first ray of light 500 forms on the screen 510 a point of light 514 , The camera 512 which has a CCD chip, for example, takes the light spot 514 on.

The measuring device 502 also has a detection device 516 on which the light point 514 with a reference light point 514 ' compares. At the reference light point 514 ' it may simply be a parameter such as a target position, which on a data memory of the detection device 516 is stored. The actual position of the light spot 514 then becomes with the reference position of the reference light point 514 ' compared. The comparison result represents, for example, an optical characteristic in the present sense. Depending on the comparison result or the optical characteristic, the determination device 516 generate output information indicating which optical elements 202A how to adjust The subsequent adjustment can be automated.

Furthermore, the measuring device 502 a robot 518 which is adapted to the light source 504 at at least two different positions P, P 'position. Thereby, two spaced light beams are generated (the second light beam is in 5B not shown for clarity). The two light beams are generated sequentially, ie one after the other. By means of the second light beam or further light beams, an accuracy associated with the 5A and 5B described reflectometric measurement, ie, the positions and orientations of the optical elements 202A can be captured even better.

The embodiment illustrating a wavefront measurement according to FIGS 6A and 6B differs from the embodiment according to the 6A and 6B in particular, that behind the exit 206 a correction optics 600 followed by the detection device 508 . 512 the latter, for example in the form of a camera, is arranged. According to the embodiment, as in 6B to see the correction optics 600 in the form of a microlens array 611 educated. Next is in 6B an electronics chip, such as a CMOS or CCD chip, the camera 512 shown.

The microlens array 611 forms light rays 500 . 602 , which are each assigned to different wavefronts, in the form of a Light dots pattern 604 comprising several points of light 514 . 608 on the camera 512 from. The correction optics 600 can be together with the camera 512 form a Shack-Hartmann sensor.

According to one embodiment, the correction optics 600 designed so that they have the effect of the second part of the lens 202B replicates. As a result, this causes a picture on the input side 212 of the first partial lens 200A at the exit side 206 is displayed correctly, here on the camera 512 , This is particularly preferably achieved in that, as in the 7A and 7B shown, the correction optics 600 furthermore a computer generated hologram 700 includes. For example, the computer-generated hologram 700 be set up to the light rays 500 . 602 to parallelize. The parallel light rays then strike the microlens array 611 in parallel. When using EUV light is used instead of the microlens array 611 an unillustrated pinhole grid preferably used (this also applies to 6B ).

On the camera 512 is in the embodiment according to the 7A and 7B in contrast to the embodiments of the 6A and 6B a regular - and not irregular - light spot pattern 604 generated. A comparison with a corresponding reference light spot pattern 604 ' then leads to the determination of the optical characteristic. For example - and this applies both to the embodiment of the 7A and 7B as well as for the embodiment of the 6A and 6B - can be a distance between points of light 514 . 608 of the light spot pattern 604 to reference light points 514 ' . 608 ' a reference light spot pattern 604 ' in the investigation facility 516 determined and by appropriate adjustment of the optical elements 202A are increasingly minimized.

For example, one of the in the 5A to 7B also described in each case in different positions of one or more optical elements 202A be performed. A corresponding optical element 202A For example, it can be actuated by means of an actuator between two different positions thereof.

Also, the measuring methods described above can be combined. For example. can first the partial lens 200A by means of the method according to 6A and 6B followed by a rough adjustment of the optical elements 202A followed by the partial lens 200A by means of the method according to 7A and 7B measured and finally a fine adjustment of the optical elements 202A be made.

After making the projection lens 104 its imaging properties are checked. Subsequent can then a surface treatment of individual optical elements 202A . 202B or a readjustment thereof via corresponding actuators or manipulators.

Although the invention has been described with reference to various embodiments, it is by no means limited thereto, but variously modifiable.

LIST OF REFERENCE NUMBERS

100

lithography system

100A

EUV lithography system

100B

DUV lithography system

102

Beam shaping and lighting system

104

projection system

106A

EUV-light source

106B

DUV light source

108A

EUV radiation

108B

DUV radiation

110

mirror

112

mirror

114

mirror

116

mirror

118

mirror

120

photomask

122

wafer

124

optical axis of the projection system

126

control device

128

Holder of the photomask

130

Holder of the wafer

132

lens

134

mirror

136

mirror

200A

partial objective

200B

partial objective

202A

optical element

202B

optical element

204A

beam path

204B

beam path

206

interface

208

beam path

210

input side

212

output side

400

partial objective

500

beam of light

502

measuring device

504

light source

506

mask

508

detector

510

focusing screen

512

camera

514

light spot

514 '

Reference light point

516

determining device

518

robot

600

corrective optics

602

beam of light

604

Light dot pattern

604 '

Reference light spot pattern

608

light spot

608 '

Reference light point

611

Microlens array

700

computer generated hologram

801 - 805

steps

a

longest distance

Claims (28)

A method of producing a lens (104) for a lithography apparatus (100), comprising the following steps: a) providing at least a first and a second partial objective (200A, 200B), wherein the at least one first partial objective (200A) comprises a plurality of optical elements (202A) and the at least one second partial objective (200B) comprises at least one optical element (202B) the at least one first and second partial objective (200A, 200B) each have a beam path (204A, 204B) which is non-homocentric on the input and / or output side (206, 210, 212) of a respective partial objective (200A, 200B) is b) transmitting at least one first light beam (500, 602) along a respective beam path (204A, 204B) of the at least one first and second sub-objective (200A, 200B) and detecting the at least one first light beam (500, 602) behind a respective sub-objective ( 200A, 200B), c) determining at least one optical characteristic of a respective partial objective (200A, 200B) on the basis of the detected, at least one first light beam (500, 602), d) adjusting the plurality of optical elements (202A) of the first partial objective (200A) and the at least one optical element (202B) of the second partial objective (200B) in dependence on the determined optical characteristic, and e) assembling the at least one first and second partial objective (200A, 200B) to produce the objective (104). Method according to Claim 1 wherein the at least one first light beam (500, 602) is detected by a detection device (508) on which it generates a light spot (514, 608), and wherein determining the at least one optical characteristic comprises comparing the light point (514, 608 ) with a reference light spot (514 ', 608'). Method according to Claim 2 wherein a position of the light spot (514, 608) is compared with a position of the reference light spot (514 ', 608'). Method according to one of Claims 1 to 3 wherein at least a first and a second light beam (500, 602) spaced therefrom are transmitted along a respective beam path (204A, 204B) of the at least one first and second sub-objective (200A, 200B) and detected behind a respective sub-objective (200A, 200B) and wherein the at least one optical characteristic is determined on the basis of the detected first and second light beams (500, 602). Method according to Claim 4 wherein the at least one first and second light beam (500, 602) is detected by a detection device (508) on which the at least one first and second light beam (500, 602) generate a light spot pattern (604), wherein the determining of the at least one optical characteristic comprises comparing the spot pattern (604) with a reference spot pattern (604 '). Method according to Claim 4 or 5 wherein the at least one first and the second light beam (500, 602) spaced therefrom are generated by moving a light source (504) between two positions (p, p '). Method according to Claim 6 wherein the light source (504) is moved between the two positions (p, p ') by means of a robot (518). Method according to one of Claims 1 to 5 , wherein the at least one first and that of this spaced second light beam (500, 602) are generated by simultaneously providing two spaced-apart light sources (504). Method according to one of Claims 1 to 8th wherein the at least one optical characteristic of at least one partial objective (200A, 200B) is determined using a deflektometric measuring method. Method according to Claim 9 in which at least one light source (504) for generating the at least one first light beam (500, 602) and a mask (506) illuminated by it in front of the at least one partial objective (200A, 200B) and a detection device (508) for the deflektometric measuring method Detecting the at least one first light beam (500, 602) behind the corresponding partial objective (200A, 200B) are arranged. Method according to one of Claims 1 to 10 wherein the at least one optical characteristic of at least one partial objective (200A, 200B) is determined using a method for wavefront measurement. Method according to Claim 11 , wherein for the method for wavefront measurement at least one light source (504) for generating the at least one first light beam (500, 602) and one of these illuminated mask (506) in front of the at least one partial objective (200A, 200B) are arranged further correction optics (600) for correcting the at least one first light beam (500, 602) is provided, and a detection means (508) for detecting the at least one first corrected light beam (500, 602) behind the corresponding part objective (200A, 200B) is arranged. Method according to Claim 12 wherein the correction optics (600) comprises a microlens array (611) or a pinhole grid. Method according to Claim 12 or 13 wherein the correction optics (600) comprises a computer-generated hologram (700). Method according to one of Claims 12 to 14 wherein the correction optics (600) for each light beam (500, 602) each comprise a computer-generated hologram (700). Method according to Claim 14 wherein the computer-generated hologram (700) is arranged in front of the microlens array (611) or the pinhole grid. Method according to Claim 14 or 16 wherein the computer-generated hologram (700) is configured to parallelize the at least one first and second light beam (500, 602). Method according to one of Claims 14 to 17 wherein the at least one optical characteristic of at least one sub-objective (200A, 200B) is determined in a first step using the method of wavefront measurement without computer-generated hologram (700) and in a second step with computer-generated hologram (700). Method according to one of Claims 2 to 18 wherein the detection means (508) is a ground glass (510) and / or an electronics chip (512). Method according to one of Claims 1 to 19 wherein the plurality of optical elements (202A) of the first partial objective (200A) and the at least one optical element (202B) of the second partial objective (200B) are fixed after step d). Method according to one of Claims 1 to 20 wherein the plurality of optical elements (202A) of the first partial objective (200A) respectively and / or the at least one optical element (202B) of the second partial objective (200B) operate between the lithography apparatus (100) between a first and a second position and / or Alignment are actuated, wherein step c) is performed in the first and second position and / or orientation. Method according to one of Claims 1 to 21 , wherein after step e) an imaging optical characteristic of the manufactured objective (104) is determined at the operating wavelength. Method according to Claim 22 in which, depending on the determined imaging optical characteristic, a post-processing of surfaces or an actuation of one or more of the optical elements (202A, 202B) of the at least one first or second partial objective (200A, 200B) takes place. Method according to one of Claims 1 to 23 in which an interface (206) in the beam path (208) between the at least one first and second partial objective (200A, 200B) is at a distance (a) between an optical element (202A) of the first partial objective (200A) and an optical element (202B). of the second sub-objective (200B), which is longer than the longest distance between each two adjacent optical elements (202A, 202B) of the at least one first and second sub-objective (200A, 200B). Method according to one of Claims 1 to 24 wherein at least three partial lenses (200A, 200B) are provided. Method according to one of Claims 1 to 25 wherein the plurality of optical elements (202A) of the first partial objective (200A) and / or the at least one optical element (202B) of the second partial objective (200B) are mirrors and / or lenses. Method according to one of Claims 1 to 26 in which two or more sub-objectives (200A, 200B) are combined to form a sub-objective (200A, 200B). Method according to Claim 27 , wherein the steps a) to e) are repeated with the combined partial objective (200A, 200B).

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